4 replies to this topic

[kwacktastic]

Hi,

I've recently bought a '96 Cooper Mpi. The factory-fitted alarm has recently developed a "fault" whereby the dashboard LED doesn't flash quickly when the alarm is activated. After thirty seconds or so of inactivity it starts flashing at the normal speed. In all other respects, the alarm appears to function correctly. The car recently had its battery removed for a week or so when it was having a new battery box welded in. I've tried removing the battery connections and re-fixing them (thinking it may have arced when reconnected) thereby allowing the alrms to discharge / reset for an hour or two. This had no effect.

Has anyone had similar problems. Moreover, can anyone offer any advice? It's not a major issue, it's just a niggle affecting an otherwise fantastic car!

Thanks in advance

Regards,

Kwack

[Gibbo]

I've got a 96' mpi cooper and the LED is crazy, ever since problems with the battery it just flashes however it wants, I've just ignored it, probably needs resetting by a rover techy or something.

[kwacktastic]

OK, it's taken me a while, but I finally got to the bottom of this problem. It turns out this was a self-inflicted fault. Let me explain...

The fault first appeared shortly after the car had some welding done. At the same time, it had a boot liner kit fitted to make the boot more presentable. This kit had an interior boot light fitted. This made use of the boot switch used by the Alarm ECU to detect when the boot has been opened. This was the cause of my problem.

Essentially, the problem was that the Alarm sensing connection was effectively grounded through the boot lamp and the exterior lights (albeit with a small resistance). This was sufficient for the alarm to think the boot lid was open and would therefore not arm that part of the circuit. After thirty seconds or so, the alarm would arm itself protecting only the doors and the bonnet.

To get round the issue, I installed two rectifier diodes (1N5404 3A devices) as shown in the circuit diagram below. Thus the diodes are reverse-biased most of the time (except when the lights are on AND the boot lid is open) meaning there is no longer a path to earth for the Alarm ECU sensing connection. Assuming the interior light is 5W, the current flowing through D1 will only ever be 0.5A or thereabouts, well below its rated value.

With the modification completed as above, the alarm operates as it should and all areas of the car are now protected.

 circuit.JPG   12.87K   12 downloads

I hope this post may help others address similar faults should they arise. Note, my car is fitted with the factory alarm, though the principles should be equally valid with an after-market device.

Regards,

Kwack

[davof]

I'm having a somehow similar problem with my mini (1996 spi).

The alarm/immobilizer led worked perfectly but now when I arm the alarm the led won't blink as it should so I can't know if the alarm is armed or not (but alarm works, when I open a door the car starts honking).

After 30 seconds or so the immobilizer connects and the red led starts blinking. If i press the fob lock button when the red led is blinking then the led goes off.

When I try to arm the alarm while there's some door opened then there's a steady red light as it should.

This has happened after the car didn't move for like 15 days and after the bonnet lid was accidentally closed quite violently (in case this could be related to the alarm problem).

The immobilizer and the alarm seems to work ok except for the LED weird behaviour.

My guess is that now the fob doesn't connect the immobilizer at the same time it arms the alarm, but I haven't check it out yet.

[davof]

Ok, I'm stupid. I had the bonnet lid opened. Now everything's ok.